Merge pull request #622 from hashicorp/f-sockets

Unix domain sockets

command/agent/agent.go

@@ -24,13 +24,6 @@ const (
 	// Path to save local agent checks
 	checksDir = "checks"
 
-	// errSocketFileExists is the human-friendly error message displayed when
-	// trying to bind a socket to an existing file.
-	errSocketFileExists = "A file exists at the requested socket path %q. " +
-		"If Consul was not shut down properly, the socket file may " +
-		"be left behind. If the path looks correct, remove the file " +
-		"and try again."
-
 	// The ID of the faux health checks for maintenance mode
 	serviceMaintCheckPrefix = "_service_maintenance"
 	nodeMaintCheckID        = "_node_maintenance"

command/agent/command.go

@@ -295,11 +295,15 @@ func (c *Command) setupAgent(config *Config, logOutput io.Writer, logWriter *log
 		return err
 	}
 
-	// Error if we are trying to bind a domain socket to an existing path
-	if path, ok := unixSocketAddr(config.Addresses.RPC); ok {
-		if _, err := os.Stat(path); err == nil || !os.IsNotExist(err) {
-			c.Ui.Output(fmt.Sprintf(errSocketFileExists, path))
-			return fmt.Errorf(errSocketFileExists, path)
+	// Clear the domain socket file if it exists
+	socketPath, isSocket := unixSocketAddr(config.Addresses.RPC)
+	if isSocket {
+		if _, err := os.Stat(socketPath); !os.IsNotExist(err) {
+			agent.logger.Printf("[WARN] agent: Replacing socket %q", socketPath)
+		}
+		if err := os.Remove(socketPath); err != nil && !os.IsNotExist(err) {
+			c.Ui.Output(fmt.Sprintf("Error removing socket file: %s", err))
+			return err
 		}
 	}
 
@@ -310,6 +314,15 @@ func (c *Command) setupAgent(config *Config, logOutput io.Writer, logWriter *log
 		return err
 	}
 
+	// Set up ownership/permission bits on the socket file
+	if isSocket {
+		if err := setFilePermissions(socketPath, config.UnixSockets); err != nil {
+			agent.Shutdown()
+			c.Ui.Error(fmt.Sprintf("Error setting up socket: %s", err))
+			return err
+		}
+	}
+
 	// Start the IPC layer
 	c.Ui.Output("Starting Consul agent RPC...")
 	c.rpcServer = NewAgentRPC(agent, rpcListener, logOutput, logWriter)

command/agent/command_test.go

@@ -6,7 +6,6 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
-	"strings"
 	"testing"
 
 	"github.com/hashicorp/consul/testutil"
@@ -166,7 +165,7 @@ func TestRetryJoinWanFail(t *testing.T) {
 	}
 }
 
-func TestSetupAgent_UnixSocket_Fails(t *testing.T) {
+func TestSetupAgent_RPCUnixSocket_FileExists(t *testing.T) {
 	conf := nextConfig()
 	tmpDir, err := ioutil.TempDir("", "consul")
 	if err != nil {
@@ -185,10 +184,12 @@ func TestSetupAgent_UnixSocket_Fails(t *testing.T) {
 	conf.Server = true
 	conf.Bootstrap = true
 
-	// Set socket address to an existing file. Consul should fail to
-	// start and return an error.
+	// Set socket address to an existing file.
 	conf.Addresses.RPC = "unix://" + socketPath
 
+	// Custom mode for socket file
+	conf.UnixSockets.Perms = "0777"
+
 	shutdownCh := make(chan struct{})
 	defer close(shutdownCh)
 
@@ -200,12 +201,22 @@ func TestSetupAgent_UnixSocket_Fails(t *testing.T) {
 	logWriter := NewLogWriter(512)
 	logOutput := new(bytes.Buffer)
 
-	// Ensure we got an error mentioning the socket file
-	err = cmd.setupAgent(conf, logOutput, logWriter)
-	if err == nil {
-		t.Fatalf("should have failed")
+	// Ensure the server is created
+	if err := cmd.setupAgent(conf, logOutput, logWriter); err != nil {
+		t.Fatalf("err: %s", err)
 	}
-	if !strings.Contains(err.Error(), socketPath) {
-		t.Fatalf("expected socket file error, got: %q", err)
+
+	// Ensure the file was replaced by the socket
+	fi, err := os.Stat(socketPath)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if fi.Mode()&os.ModeSocket == 0 {
+		t.Fatalf("expected socket to replace file")
+	}
+
+	// Ensure permissions were applied to the socket file
+	if fi.Mode().String() != "Srwxrwxrwx" {
+		t.Fatalf("bad permissions: %s", fi.Mode())
 	}
 }

command/agent/config.go

@@ -343,6 +343,35 @@ type Config struct {
 
 	// WatchPlans contains the compiled watches
 	WatchPlans []*watch.WatchPlan `mapstructure:"-" json:"-"`
+
+	// UnixSockets is a map of socket configuration data
+	UnixSockets UnixSocketConfig `mapstructure:"unix_sockets"`
+}
+
+// UnixSocketPermissions contains information about a unix socket, and
+// implements the FilePermissions interface.
+type UnixSocketPermissions struct {
+	Usr   string `mapstructure:"user"`
+	Grp   string `mapstructure:"group"`
+	Perms string `mapstructure:"mode"`
+}
+
+func (u UnixSocketPermissions) User() string {
+	return u.Usr
+}
+
+func (u UnixSocketPermissions) Group() string {
+	return u.Grp
+}
+
+func (u UnixSocketPermissions) Mode() string {
+	return u.Perms
+}
+
+// UnixSocketConfig stores information about various unix sockets which
+// Consul creates and uses for communication.
+type UnixSocketConfig struct {
+	UnixSocketPermissions `mapstructure:",squash"`
 }
 
 // unixSocketAddr tests if a given address describes a domain socket,
@@ -889,6 +918,15 @@ func MergeConfig(a, b *Config) *Config {
 	if b.DisableAnonymousSignature {
 		result.DisableAnonymousSignature = true
 	}
+	if b.UnixSockets.Usr != "" {
+		result.UnixSockets.Usr = b.UnixSockets.Usr
+	}
+	if b.UnixSockets.Grp != "" {
+		result.UnixSockets.Grp = b.UnixSockets.Grp
+	}
+	if b.UnixSockets.Perms != "" {
+		result.UnixSockets.Perms = b.UnixSockets.Perms
+	}
 
 	if len(b.HTTPAPIResponseHeaders) != 0 {
 		if result.HTTPAPIResponseHeaders == nil {

command/agent/config_test.go

@@ -588,6 +588,23 @@ func TestDecodeConfig(t *testing.T) {
 		t.Fatalf("bad: %#v", config)
 	}
 
+	// Domain socket permissions
+	input = `{"unix_sockets": {"user": "500", "group": "500", "mode": "0700"}}`
+	config, err = DecodeConfig(bytes.NewReader([]byte(input)))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if config.UnixSockets.Usr != "500" {
+		t.Fatalf("bad: %#v", config)
+	}
+	if config.UnixSockets.Grp != "500" {
+		t.Fatalf("bad: %#v", config)
+	}
+	if config.UnixSockets.Perms != "0700" {
+		t.Fatalf("bad: %#v", config)
+	}
+
 	// Disable updates
 	input = `{"disable_update_check": true, "disable_anonymous_signature": true}`
 	config, err = DecodeConfig(bytes.NewReader([]byte(input)))
@@ -1034,6 +1051,13 @@ func TestMergeConfig(t *testing.T) {
 		HTTPAPIResponseHeaders: map[string]string{
 			"Access-Control-Allow-Origin": "*",
 		},
+		UnixSockets: UnixSocketConfig{
+			UnixSocketPermissions{
+				Usr:   "500",
+				Grp:   "500",
+				Perms: "0700",
+			},
+		},
 	}
 
 	c := MergeConfig(a, b)

command/agent/http.go

@@ -96,9 +96,13 @@ func NewHTTPServers(agent *Agent, config *Config, logOutput io.Writer) ([]*HTTPS
 		}
 
 		// Error if we are trying to bind a domain socket to an existing path
-		if path, ok := unixSocketAddr(config.Addresses.HTTP); ok {
-			if _, err := os.Stat(path); err == nil || !os.IsNotExist(err) {
-				return nil, fmt.Errorf(errSocketFileExists, path)
+		socketPath, isSocket := unixSocketAddr(config.Addresses.HTTP)
+		if isSocket {
+			if _, err := os.Stat(socketPath); !os.IsNotExist(err) {
+				agent.logger.Printf("[WARN] agent: Replacing socket %q", socketPath)
+			}
+			if err := os.Remove(socketPath); err != nil && !os.IsNotExist(err) {
+				return nil, fmt.Errorf("error removing socket file: %s", err)
 			}
 		}
 
@@ -113,6 +117,13 @@ func NewHTTPServers(agent *Agent, config *Config, logOutput io.Writer) ([]*HTTPS
 			list = tcpKeepAliveListener{ln.(*net.TCPListener)}
 		}
 
+		// Set up ownership/permission bits on the socket file
+		if isSocket {
+			if err := setFilePermissions(socketPath, config.UnixSockets); err != nil {
+				return nil, fmt.Errorf("Failed setting up HTTP socket: %s", err)
+			}
+		}
+
 		// Create the mux
 		mux := http.NewServeMux()
 

command/agent/http_test.go

@@ -67,6 +67,11 @@ func TestHTTPServer_UnixSocket(t *testing.T) {
 
 	dir, srv := makeHTTPServerWithConfig(t, func(c *Config) {
 		c.Addresses.HTTP = "unix://" + socket
+
+		// Only testing mode, since uid/gid might not be settable
+		// from test environment.
+		c.UnixSockets = UnixSocketConfig{}
+		c.UnixSockets.Perms = "0777"
 	})
 	defer os.RemoveAll(dir)
 	defer srv.Shutdown()
@@ -77,6 +82,15 @@ func TestHTTPServer_UnixSocket(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
+	// Ensure the mode was set properly
+	fi, err := os.Stat(socket)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if fi.Mode().String() != "Srwxrwxrwx" {
+		t.Fatalf("bad permissions: %s", fi.Mode())
+	}
+
 	// Ensure we can get a response from the socket.
 	path, _ := unixSocketAddr(srv.agent.config.Addresses.HTTP)
 	client := &http.Client{
@@ -132,11 +146,17 @@ func TestHTTPServer_UnixSocket_FileExists(t *testing.T) {
 	defer os.RemoveAll(dir)
 
 	// Try to start the server with the same path anyways.
-	if servers, err := NewHTTPServers(agent, conf, agent.logOutput); err == nil {
-		for _, server := range servers {
-			server.Shutdown()
+	if _, err := NewHTTPServers(agent, conf, agent.logOutput); err != nil {
+		t.Fatalf("err: %s", err)
 	}
-		t.Fatalf("expected socket binding error")
+
+	// Ensure the file was replaced by the socket
+	fi, err = os.Stat(socket)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if fi.Mode()&os.ModeSocket == 0 {
+		t.Fatalf("expected socket to replace file")
 	}
 }
 

command/agent/util.go

@@ -9,7 +9,9 @@ import (
 	"math/rand"
 	"os"
 	"os/exec"
+	"os/user"
 	"runtime"
+	"strconv"
 	"time"
 
 	"github.com/hashicorp/go-msgpack/codec"
@@ -97,3 +99,65 @@ func encodeMsgPack(msg interface{}) ([]byte, error) {
 func stringHash(s string) string {
 	return fmt.Sprintf("%x", md5.Sum([]byte(s)))
 }
+
+// FilePermissions is an interface which allows a struct to set
+// ownership and permissions easily on a file it describes.
+type FilePermissions interface {
+	// User returns a user ID or user name
+	User() string
+
+	// Group returns a group ID. Group names are not supported.
+	Group() string
+
+	// Mode returns a string of file mode bits e.g. "0644"
+	Mode() string
+}
+
+// setFilePermissions handles configuring ownership and permissions settings
+// on a given file. It takes a path and any struct implementing the
+// FilePermissions interface. All permission/ownership settings are optional.
+// If no user or group is specified, the current user/group will be used. Mode
+// is optional, and has no default (the operation is not performed if absent).
+// User may be specified by name or ID, but group may only be specified by ID.
+func setFilePermissions(path string, p FilePermissions) error {
+	var err error
+	uid, gid := os.Getuid(), os.Getgid()
+
+	if p.User() != "" {
+		if uid, err = strconv.Atoi(p.User()); err == nil {
+			goto GROUP
+		}
+
+		// Try looking up the user by name
+		if u, err := user.Lookup(p.User()); err == nil {
+			uid, _ = strconv.Atoi(u.Uid)
+			goto GROUP
+		}
+
+		return fmt.Errorf("invalid user specified: %v", p.User())
+	}
+
+GROUP:
+	if p.Group() != "" {
+		if gid, err = strconv.Atoi(p.Group()); err != nil {
+			return fmt.Errorf("invalid group specified: %v", p.Group())
+		}
+	}
+	if err := os.Chown(path, uid, gid); err != nil {
+		return fmt.Errorf("failed setting ownership to %d:%d on %q: %s",
+			uid, gid, path, err)
+	}
+
+	if p.Mode() != "" {
+		mode, err := strconv.ParseUint(p.Mode(), 8, 32)
+		if err != nil {
+			return fmt.Errorf("invalid mode specified: %v", p.Mode())
+		}
+		if err := os.Chmod(path, os.FileMode(mode)); err != nil {
+			return fmt.Errorf("failed setting permissions to %d on %q: %s",
+				mode, path, err)
+		}
+	}
+
+	return nil
+}

command/agent/util_test.go

@@ -1,6 +1,8 @@
 package agent
 
 import (
+	"io/ioutil"
+	"os"
 	"testing"
 	"time"
 )
@@ -39,3 +41,59 @@ func TestStringHash(t *testing.T) {
 		t.Fatalf("bad: %s", out)
 	}
 }
+
+func TestSetFilePermissions(t *testing.T) {
+	tempFile, err := ioutil.TempFile("", "consul")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	path := tempFile.Name()
+	defer os.Remove(path)
+
+	// Bad UID fails
+	if err := setFilePermissions(path, UnixSocketPermissions{Usr: "%"}); err == nil {
+		t.Fatalf("should fail")
+	}
+
+	// Bad GID fails
+	if err := setFilePermissions(path, UnixSocketPermissions{Grp: "%"}); err == nil {
+		t.Fatalf("should fail")
+	}
+
+	// Bad mode fails
+	if err := setFilePermissions(path, UnixSocketPermissions{Perms: "%"}); err == nil {
+		t.Fatalf("should fail")
+	}
+
+	// Allows omitting user/group/mode
+	if err := setFilePermissions(path, UnixSocketPermissions{}); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Doesn't change mode if not given
+	if err := os.Chmod(path, 0700); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if err := setFilePermissions(path, UnixSocketPermissions{}); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	fi, err := os.Stat(path)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if fi.Mode().String() != "-rwx------" {
+		t.Fatalf("bad: %s", fi.Mode())
+	}
+
+	// Changes mode if given
+	if err := setFilePermissions(path, UnixSocketPermissions{Perms: "0777"}); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	fi, err = os.Stat(path)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if fi.Mode().String() != "-rwxrwxrwx" {
+		t.Fatalf("bad: %s", fi.Mode())
+	}
+}

website/source/docs/agent/options.html.markdown

@@ -244,8 +244,10 @@ definitions support being updated during a reload.
   Both `rpc` and `http` support binding to Unix domain sockets. A socket can be
   specified in the form `unix:///path/to/socket`. A new domain socket will be
   created at the given path. If the specified file path already exists, Consul
-  will refuse to start and return an error. For information on how to secure
-  socket file permissions, refer to the manual page for your operating system.
+  will attempt to clear the file and create the domain socket in its place.
+  <br><br>
+  The permissions of the socket file are tunable via the `unix_sockets` config
+  construct.
   <br><br>
   When running Consul agent commands against Unix socket interfaces, use the
   `-rpc-addr` or `-http-addr` arguments to specify the path to the socket. You
@@ -429,6 +431,23 @@ definitions support being updated during a reload.
 
 * `ui_dir` - Equivalent to the `-ui-dir` command-line flag.
 
+* `unix_sockets` - This allows tuning the ownership and permissions of the
+  Unix domain socket files created by Consul. Domain sockets are only used if
+  the HTTP or RPC addresses are configured with the `unix://` prefix. The
+  following options are valid within this construct, and apply globally to all
+  sockets created by Consul:
+  <br>
+  * `user` - The name or ID of the user who will own the socket file.
+  * `group` - The group ID ownership of the socket file. Note that this option
+    currently only supports numeric ID's.
+  * `mode` - The permission bits to set on the file.
+  <br>
+  It is important to note that this option may have different effects on
+  different operating systems. Linux generally observes socket file permissions,
+  while many BSD variants ignore permissions on the socket file itself. It is
+  important to test this feature on your specific distribution. This feature is
+  currently not functional on Windows hosts.
+
 * `verify_incoming` - If set to True, Consul requires that all incoming
   connections make use of TLS, and that the client provides a certificate signed
   by the Certificate Authority from the `ca_file`. By default, this is false, and